function s_out=alamouti(s_in)
%assume length is 2

for k=1:size(s_in,2)
	s_out(:,2*k-1)=s_in(:,k);
	s_out(:,2*k)=orthogonalize(s_in(:,k));
end



function y=orthogonalize(x)

y(1)=-1*conj(x(2));
y(2)=conj(x(1));



